diff options
| author | Alvaro Herrera | 2017-04-06 15:27:15 +0000 |
|---|---|---|
| committer | Alvaro Herrera | 2017-04-06 15:28:50 +0000 |
| commit | b1fc51a36ecdf854be9e41ffb99953c40ef96ccf (patch) | |
| tree | a0ca63f53d93cfb85baf55ec2ec8e898b68e584f /src/backend/statistics | |
| parent | dc0400cc501ebe839c15a387911945d1585e4787 (diff) | |
Comment fixes for extended statistics
Clean up some code comments in new extended statistics code, from
7b504eb282.
Diffstat (limited to 'src/backend/statistics')
| -rw-r--r-- | src/backend/statistics/dependencies.c | 9 | ||||
| -rw-r--r-- | src/backend/statistics/extended_stats.c | 7 |
2 files changed, 11 insertions, 5 deletions
diff --git a/src/backend/statistics/dependencies.c b/src/backend/statistics/dependencies.c index fb958e1b0a5..159ddb87233 100644 --- a/src/backend/statistics/dependencies.c +++ b/src/backend/statistics/dependencies.c @@ -900,7 +900,13 @@ find_strongest_dependency(StatisticExtInfo * stats, MVDependencies * dependencie /* * dependencies_clauselist_selectivity - * Attempt to estimate selectivity using functional dependency statistics + * Return the estimated selectivity of the given clauses using + * functional dependency statistics, or 1.0 if no useful functional + * dependency statistic exists. + * + * 'estimatedclauses' is an output argument that gets a bit set corresponding + * to the (zero-based) list index of clauses that are included in the + * estimated selectivity. * * Given equality clauses on attributes (a,b) we find the strongest dependency * between them, i.e. either (a=>b) or (b=>a). Assuming (a=>b) is the selected @@ -935,7 +941,6 @@ dependencies_clauselist_selectivity(PlannerInfo *root, AttrNumber *list_attnums; int listidx; - /* check if there's any stats that might be useful for us. */ if (!has_stats_of_kind(rel->statlist, STATS_EXT_DEPENDENCIES)) return 1.0; diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c index 006bb897c48..4b3aa778140 100644 --- a/src/backend/statistics/extended_stats.c +++ b/src/backend/statistics/extended_stats.c @@ -408,7 +408,7 @@ multi_sort_compare_dims(int start, int end, /* * has_stats_of_kind - * Check that the list contains statistic of a given kind + * Check that the list contains statistic of a given kind */ bool has_stats_of_kind(List *stats, char requiredkind) @@ -428,8 +428,9 @@ has_stats_of_kind(List *stats, char requiredkind) /* * choose_best_statistics - * Look for statistics with the specified 'requiredkind' which have keys - * that match at least two attnums. + * Look for and return statistics with the specified 'requiredkind' which + * have keys that match at least two of the given attnums. Return NULL if + * there's no match. * * The current selection criteria is very simple - we choose the statistics * referencing the most attributes with the least keys. |